Automated ultrasonic inspection of elongated composite members using single-pass robotic system

ABSTRACT

Apparatus and methods for ultrasonic inspection of elongated composite members in a single scan pass using pulse echo phased arrays operating in a bubbler method. The system concept is fully automated by integrating an inspection probe assembly to a robot and using the robot to move the inspection probe assembly along the part (i.e., outside of an inspection tank); and by integrating tooling fixtures that move out of the way as the inspection probe assembly travels along the length of the part during the inspection. In addition, the system allows for generally elongated composite members having lengthwise variation in shape, curvature and dimensions.

RELATED PATENT APPLICATIONS

This application is a divisional of and claims priority from U.S. patentapplication Ser. No. 14/836,154 filed on Aug. 26, 2015, which issued asU.S. Pat. No. 9,933,396 on Apr. 3, 2018.

BACKGROUND

This disclosure generally relates to non-destructive inspectionequipment and methods, and relates more particularly to methods andapparatus for inspecting elongated members, such as stiffeners, made ofcomposite material.

Non-destructive inspection of structures involves thoroughly examining astructure without harming the structure or requiring its significantdisassembly. Non-destructive inspection is commonly used in the aircraftindustry to inspect aircraft structures for any type of anomaly in thestructure. Non-destructive inspection is also used in the initialfabrication of the aircraft's structural components. It is used toassure that a part was fabricated correctly and to ensure that noforeign material was embedded within the part. Inspection may beperformed during manufacturing of a structure and/or after a structurehas been put in service

Non-destructive inspection (NDI) may be performed on stiffened compositeparts of an aircraft. Composite parts such as fuselages and wings arefrequently stiffened using elongated composite members called“stringers”. These stiffeners may be made of a composite material suchas carbon fiber-reinforced plastic (CFRP). As used herein, the term“elongated composite members” includes but is not limited to compositestiffeners used in the construction of fuselages and wings of aircraft,such as wing blade stiffeners and wing vent stiffeners.

More specifically, the quality of a stiffener can be determinednon-destructively by ultrasonic testing. A stiffener can be inspectedultrasonically by a probe, including one or more shoes that holdrespective ultrasonic transducer arrays, that is moved incrementallyalong the length of the stiffener. As the probe is being moved, thetransducer arrays may operate in pulse/echo mode to generate pulsedultrasonic waves, which propagate into the stiffener. Reflectedultrasonic waves are returned to and detected by the ultrasonictransducer arrays to provide data indicative of the presence ofanomalies in the stiffener. Data acquired by the ultrasonic transducerarrays is typically processed by a computer system, and the processeddata may be presented to a user via a computer monitor. A dataacquisition device and data handling software may be used for collectionand display of inspection data, such as displaying the data on acomputer monitor as an image representation of the structure underinspection, such as a stringer, supplemented with corresponding colorand/or graphical data of the inspection to permit examination by aqualified inspector.

Automated inspection systems typically employ a manipulator (e.g.,overhead gantry, multi-axis scanner, or robot) that scans an NDI endeffector along the part being inspected. For single-sided inspectionmethods, such as pulse echo ultrasonic inspection, a single-arm roboticdevice having multiple degrees of freedom may be used to position andmove an NDI end effector, such as a pulse echo ultrasonic inspectiondevice, attached to the end of the robot arm.

Some stiffeners incorporated in aircraft wings are inspected in largeimmersion tanks, which can have an impact on overall manufacturingthroughput and on the required factory floor space for the inspectionsystem. In a feed-through immersion system, stiffeners may move throughthe inspection probes by keeping the probes relatively stationary insidea small immersion tank. This process requires the system to be twice aslong as the part because the part must be fed into one side of theimmersion tank and then exit the other side.

It would be advantageous to provide a single-pass NDI system designed sothat the part can remain stationary during inspection, thereby reducingthe inspection time required and the amount of factory space occupied bythe inspection station.

SUMMARY

The subject matter disclosed in detail below is directed to methods andapparatus for ultrasonic inspection of elongated composite members in asingle scan pass using pulse echo phased arrays operating in a bubblermethod. The system concept is fully automated by integrating aninspection probe assembly to a robot and using the robot to move theinspection probe assembly along the part (i.e., outside of an inspectiontank); and by integrating tooling fixtures that move out of the way asthe inspection probe assembly travels along the length of the partduring the inspection. The embodiments disclosed in detail below enablehigh production rates by providing a single-pass NDI system designed toinspect a part while it is stationary. This feature will reduce theamount of factory space used. In addition, incorporating robotictechnology into the inspection provides a fully automated inspection toreduce or eliminate operator fatigue.

In addition, the system allows for elongated composite members havinglengthwise variation in shape, curvature and dimensions. The ultrasonicinspection apparatus disclosed herein has enough degrees of freedom toallow for local part movements in the roll, pitch, yaw, lateral andelevation directions while still maintaining proper probe alignment tothe part.

For the purpose of illustration and explanation, apparatus and methodsfor ultrasonic inspection of a generally T-shaped wing blade stiffenerin a single scan pass (hereinafter “single pass”) will be described indetail hereinafter. However, some of the principles and conceptsembodied by the apparatus disclosed hereinafter can be applied inultrasonic inspection of other elongated composite members havingprofiles that are not generally T-shaped.

In the case where the elongated composite member is a wing bladestiffener comprising a flange intersected by a web to form radiusedportions (a.k.a. “radii”) on both sides of the intersection, anultrasonic inspection tool head is provided that comprises two phasedlinear ultrasonic transducer arrays for inspecting the flange, twophased linear ultrasonic transducer arrays for inspecting the web, andtwo phased curved ultrasonic transducer arrays for inspecting theradiused portions.

Conventional composite structure cured with hard tooling results incomposite radii that are well defined and repeatable. In contrast, thecomposite radii formed using soft tooling are not always well definedand may vary from part to part. In some cases, dimensional or contourvariations may be greater than those that would result from using hardtooling. These larger variations make reliable inspection moredifficult. In view of the deviation from circularity of soft-tooledcomposite radii, the term “radius” as used hereinafter should beconstrued non-strictly to include non-circular profiles.

The system for inspecting blade stiffeners is designed to allow theposition and orientation of the ultrasonic inspection tool head toadjust for changing web-flange angle, web height, flange width,thickness, or contour in an elevational or lateral direction (e.g.,curvature to reflect the shape of a wing skin). In a preferredembodiment, the system allows the web-flange angle to change by ±15°. Inone possible implementation, a linear variable differential transformer(LVDT) can be integrated into the inspection probe assembly. The outputfrom the LVDT is used to dynamically control robot movement, therebyaccommodating large changes in the contour or curvature of the bladestiffener along its length.

One aspect of the subject matter disclosed in detail below is anapparatus comprising: a frame; first and second rotatable shafts whichare mutually coaxial and rotatable relative to the frame; and a probehousing assembly clamped to the first and second rotatable shafts,wherein the probe housing assembly comprises: a first probe platformclamped to the first and second rotatable shafts; a second probeplatform; first and second linear slides configured to translatablycouple the second probe platform to the first probe platform; a thirdprobe platform; and third and fourth linear slides configured totranslatably couple the third probe platform to the first probeplatform. In embodiments wherein the frame comprises first throughfourth guide shafts, the apparatus further comprises a first bearingblock assembly translatably coupled to the first and second guideshafts, and a second bearing block assembly translatably coupled to thethird and fourth guide shafts, wherein the first rotatable shaft isrotatably coupled to the first bearing block assembly, and the secondrotatable shaft is rotatably coupled to the second bearing blockassembly. The apparatus may further comprise a gimbal assembly, whereinthe frame is mounted to the gimbal assembly, and the gimbal assemblycomprises a connector configured to be attached to a connector of arobot, a revolute joint supported by the connector, a thrust bearing,and fifth and sixth linear slides configured to translatably couple thethrust bearing to the revolute joint.

In accordance with some embodiments, the apparatus described in thepreceding paragraph further comprises: a first web probe translatablycoupled to the third probe platform for translation along first andsecond axes which are mutually perpendicular, the first web probecomprising a first linear ultrasonic transducer array; a second webprobe translatably coupled to the third probe platform for translationalong third and fourth axes which are mutually perpendicular, the secondweb probe comprising a second linear ultrasonic transducer array whichis parallel to the first linear ultrasonic transducer array. The firstweb probe may be rotatably coupled to the third probe platform forrotation about a fifth axis which is perpendicular to the first andsecond axes, and the second web probe may be rotatably coupled to thethird probe platform for rotation about a sixth axis which isperpendicular to the third and fourth axes. In one possibleimplementation, the apparatus further comprises: an L-shaped membercomprising first and second legs that form a right angle; a fifth linearslide configured to translatably couple the first leg of the L-shapedmember to the first web probe to enable translation along a length ofthe first leg; and a second linear slide configured to translatablycouple the second leg of the L-shaped member to the first web probe toenable translation along a length of the second leg, wherein the firstand second linear ultrasonic transducer arrays stay mutually paralleland displace relative to each other during rotation in tandem about thefirst and second axes respectively.

In accordance with the same embodiments, the apparatus furthercomprises: a first radius probe translatably coupled to the second probeplatform for translation along first and second axes which are mutuallyperpendicular, the first radius probe comprising a first curvedultrasonic transducer array; and a second radius probe translatablycoupled to the second probe platform for translation along third andfourth axes which are mutually perpendicular, the second radius probecomprising a second curved ultrasonic transducer array.

In accordance with the same embodiments, the apparatus furthercomprises: a third linear ultrasonic transducer array housed in thefirst probe platform; and a dry acoustic couplant material separatedfrom the first linear ultrasonic transducer array by a gap, wherein theprobe housing assembly further comprises: a dry acoustic couplanthousing translatably coupled to the first probe platform for translationalong first and second axes which are mutually perpendicular, the dryacoustic couplant housing supporting the dry acoustic couplant material.Optionally a second linear ultrasonic transducer array may be housed inthe first probe platform.

In accordance with some embodiments, the apparatus further comprises: afirst web probe translatably coupled to one of the first through thirdprobe platforms for translation along first and second axes which aremutually perpendicular, the first web probe comprising a first linearultrasonic transducer array; a second web probe translatably coupled tothe one of the first through third probe platforms for translation alongthird and fourth axes which are mutually perpendicular, the second webprobe comprising a second linear ultrasonic transducer array which isparallel to the first linear ultrasonic transducer array; a first radiusprobe translatably coupled to another of the first through third probeplatforms for translation along fifth and sixth axes which are mutuallyperpendicular, the first radius probe comprising a first curvedultrasonic transducer array; and a second radius probe translatablycoupled to the another of the first through third probe platforms fortranslation along seventh and eighth axes which are mutuallyperpendicular, the second radius probe comprising a second curvedultrasonic transducer array.

The apparatus described in the preceding paragraph may further comprise:a third linear ultrasonic transducer array housed in a further one ofthe first through third probe platforms; and a dry acoustic couplantmaterial separated from the third linear ultrasonic transducer array bya gap, wherein the probe housing assembly further comprises: a dryacoustic couplant housing translatably coupled to the further one of thefirst through third probe platforms for translation along ninth andtenth axes which are mutually perpendicular, the dry acoustic couplanthousing supporting the dry acoustic couplant material.

The first, second and third linear ultrasonic transducer arrays and thefirst and second curved ultrasonic transducer arrays are arranged sothat the first and second linear ultrasonic transducer arrays caninterrogate a web portion of an elongated composite member having agenerally T-shaped profile, while the first and second curved ultrasonictransducer arrays can interrogate respective radiused portions of theelongated composite member, and the third linear ultrasonic transducerarray can interrogate a first flange portion of the elongated compositemember in a single pass. Optionally a fourth linear ultrasonictransducer array may be provided for interrogating a second flangeportion of the elongated composite member.

Another aspect of the subject matter disclosed in detail below is anapparatus comprising: a probe housing assembly; a first web proberotatably coupled to the probe housing assembly for rotation about afirst axis, the first web probe comprising a first linear ultrasonictransducer array; a second web probe rotatably coupled to the probehousing assembly for rotation about a second axis which is parallel tothe first axis, the second web probe comprising a second linearultrasonic transducer array which is parallel to the first linearultrasonic transducer array; an L-shaped member comprising first andsecond legs that form a right angle; a first linear slide configured totranslatably couple the first leg of the L-shaped member to the firstweb probe to enable translation along a length of the first leg; and asecond linear slide configured to translatably couple the second leg ofthe L-shaped member to the first web probe to enable translation along alength of the second leg, wherein the first and second linear ultrasonictransducer arrays stay mutually parallel and displace relative to eachother during rotation in tandem about the first and second axesrespectively. In accordance with some embodiments, the probe housingassembly comprises: a left pivot support carriage which is rotatablycoupled to the first web probe; a first slide bracket assembly; thirdand fourth linear slides configured to translatably couple the firstslide bracket assembly to the left pivot support carriage; a right pivotsupport carriage which is rotatably coupled to the second web probe; asecond slide bracket assembly; and fifth and sixth linear slidesconfigured to translatably couple the second slide bracket assembly tothe right pivot support carriage; wherein the left and right pivotsupport carriages are slidable along third and fourth axes respectively,the third and fourth axes being perpendicular to the first and secondaxes. The probe housing assembly may further comprise: a web probeplatform; seventh and eighth linear slides configured to translatablycouple the first slide bracket assembly to the web probe platform; andninth and tenth linear slides configured to translatably couple thesecond slide bracket assembly to the web probe platform, wherein thefirst and second slide bracket assemblies are slidable along fifth andsixth axes respectively, the fifth axis being perpendicular to the firstand third axes, and the sixth axis being perpendicular to the second andfourth axes.

The apparatus described in the preceding paragraph may further comprisea frame and first and second rotatable shafts which are mutually coaxialand rotatable relative to the frame, wherein the probe housing assemblyis clamped to the first and second rotatable shafts. In accordance withsome embodiments, the frame comprises first through fourth guide shafts,the apparatus further comprising a first bearing block assemblytranslatably coupled to the first and second guide shafts, and a secondbearing block assembly translatably coupled to the third and fourthguide shafts, wherein the first rotatable shaft is rotatably coupled tothe first bearing block assembly, and the second rotatable shaft isrotatably coupled to the second bearing block assembly.

The probe housing assembly may further comprise: a flange probe platformclamped to the first and second rotatable shafts; eleventh and twelfthlinear slides configured to translatably couple the web probe platformto the flange probe platform, the apparatus further comprising a thirdlinear ultrasonic transducer array housed in the flange probe platform.In embodiments wherein the apparatus further comprises a dry acousticcouplant material separated from the third linear ultrasonic transducerarray by a gap, the probe housing assembly may further comprise: a dryacoustic couplant housing which supports the dry acoustic couplantmaterial; a third slide bracket assembly; fifteenth and sixteenth linearslides configured to translatably couple the third slide bracketassembly to the dry acoustic couplant housing; and seventeenth andeighteenth linear slides configured to translatably couple the thirdslide bracket assembly to the radius probe platform. The probe housingassembly may further comprise: a radius probe platform, and thirteenthand fourteenth linear slides configured to translatably couple theradius probe platform to the flange probe platform, in which case theapparatus further comprises first and second radius probes translatablycoupled to the radius probe platform, wherein the first and secondradius probes comprise respective curved ultrasonic transducer arrays.In addition, the probe housing assembly may further comprise: a thirdslide bracket assembly; fifteenth and sixteenth linear slides configuredto translatably couple the third bracket assembly to the first radiusprobe; seventeenth and eighteenth linear slides configured totranslatably couple the third slide bracket assembly to the radius probeplatform; a fourth slide bracket assembly; nineteenth and twentiethlinear slides configured to translatably couple the fourth bracketassembly to the second radius probe; and twenty-first and twenty-secondlinear slides configured to translatably couple the fourth slide bracketassembly to the radius probe platform.

A further aspect of the disclosed subject matter is a method forautomated ultrasonic inspection of a stationary elongated compositemember in a single pass, comprising: supporting the elongated compositemember using a multiplicity of holding fixtures disposed at intervalsalong a length of the elongated composite member, each holding fixturehaving an extended position in which the elongated composite member issupported and a retracted position in which the holding fixture isseparated from the elongated composite structure; moving an inspectionprobe assembly along a length of the elongated composite member from oneend of the elongated composite member to another end of the elongatedcomposite member, the probe assembly comprising a multiplicity ofultrasonic transducer arrays; concurrently ultrasonically inspectingweb, flange and radiused portions of the elongated composite memberusing the multiplicity of ultrasonic transducer arrays as the inspectionprobe assembly moves along the length of the elongated composite member;moving each holding fixture to its retracted position in sequence toallow the probe assembly to pass by; and extending each retractedholding fixture back to its extended position after the probe assemblyhas passed by. This method may further comprise: adjusting the positionsof the multiplicity of ultrasonic transducer arrays to take into accountvariations in the shape and location of the elongated composite memberalong its length as the inspection probe assembly moves along the lengthof the elongated composite member. In particular, the respective anglesof first and second linear ultrasonic transducer arrays can be adjustedas an angle between web and flange portions of the elongated compositemember changes along its length, while an elevation of an end effectorassembly that supports the inspection probe assembly is adjusted as acurvature of the elongated composite member in an elevation directionchanges along its length.

Other aspects of methods and apparatus for inspecting elongatedcomposite members are disclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a representative profile of a compositeblade stiffener. The profile typically varies from a true T-shape as theweb angle diverges from perpendicular along the length of the bladestiffener.

FIG. 2 is a diagram representing an isometric view of an ultrasonicinspection tool head in accordance with one embodiment, mounted to agenerally T-shaped blade stiffener.

FIG. 2A is a diagram representing an elevational view of an end effectorassembly incorporated in the tool head depicted in FIG. 2.

FIG. 2B is a diagram showing portions of an end effector assembly havinga bearing block assembly translatably coupled thereto, which componentsare incorporated in the tool head depicted in FIG. 2.

FIG. 2C is a diagram representing a sectional view taken along a planethat bisects a rotatable shaft rotatably coupled to the bearing blockassembly depicted in FIG. 2B.

FIG. 3 is a diagram representing an elevational view of the ultrasonicinspection tool head depicted in FIG. 2 mounted to a robot.

FIG. 3A is a diagram representing an elevational view of a gimbalassembly incorporated in the tool head depicted in FIG. 2.

FIG. 3B is a diagram representing an exploded view of the gimbalassembly depicted in FIG. 3A.

FIG. 4 is a diagram representing an isometric view of an inspectionprobe assembly incorporated in the tool head depicted in FIG. 2.

FIG. 5 is a diagram representing an elevational view of the inspectionprobe assembly depicted in FIG. 4.

FIG. 6 is a diagram representing a side elevational view of a web probesubassembly incorporated in the inspection probe assembly depicted inFIG. 4.

FIG. 6A is a diagram representing an isometric view of a pivot supportcarriage incorporated in the web probe subassembly depicted in FIG. 6.

FIG. 7 is a diagram representing an elevational view of a pair of linearultrasonic transducer arrays disposed on opposite sides of a web of ablade stiffener.

FIG. 8 is a diagram representing a sectional view of a radius probesubassembly incorporated in the inspection probe assembly depicted inFIG. 4.

FIGS. 9A and 9B are respective sectional views of a flange probesubassembly incorporated in the inspection probe assembly depicted inFIG. 4. In FIG. 9A, the section is taken through a first linearultrasonic transducer array; in FIG. 9B, the section is taken through asecond linear ultrasonic transducer array.

FIG. 10 is a diagram representing an isometric view of a run-on toolmounted to an outboard end of a blade stiffener.

FIG. 11 is a diagram representing an isometric view of the inspectionprobe assembly depicted in FIG. 4 mounted to the run-on tool depicted inFIG. 10.

FIG. 12 is a diagram representing an isometric view of a workcell forautomated single-pass ultrasonic inspection of a curved blade stiffenersupported by retractable holding fixtures in accordance with oneembodiment.

FIG. 13 is a flow diagram of an aircraft production and servicemethodology.

FIG. 14 is a block diagram showing systems of an aircraft.

Reference will hereinafter be made to the drawings in which similarelements in different drawings bear the same reference numerals.

DETAILED DESCRIPTION

Embodiments of apparatus and methods for ultrasonic inspection ofelongated composite members will now be described with reference to theinspection of generally T-shaped wing blade stiffeners. However, theapparatus and methods disclosed herein may also be used toultrasonically inspect composite stiffeners having other profiles andelongated composite members other than stiffeners.

FIG. 1 is a diagram showing a representative profile of a compositeblade stiffener 2 comprising a flange 4 and a web 6 that intersectsflange 4. In the area of the intersection, the blade stiffener has leftand right radiused portions 8 a and 8 b. Although not apparent from FIG.1, it should be appreciated that blade stiffener 2 may have a profilethat varies along its length. At some locations, the profile may beT-shaped; at other locations the profile may vary from T-shaped, e.g.,the web-flange angle θ diverges from 90° along the length of bladestiffener 2 (as depicted in FIG. 1). For example, the web-flange angle θmay change by ±15°. A blade stiffener profile having a web angle in thisrange will be referred to herein as a “generally T-shaped bladestiffener”.

The blade stiffener 2 can be inspected in one pass using an ultrasonicinspection tool head 10 of the type depicted in FIG. 2. The ultrasonicinspection tool head 10 is mounted to the blade stiffener 2. Inaccordance with the embodiment depicted in FIG. 2, the ultrasonicinspection tool head 10 comprises an end effector assembly 12 and aninspection probe assembly 14 that is carried by the end effectorassembly 12. The end effector assembly 12 comprises a quick-releasetool-side connector plate 16, an upper frame 20, and a gimbal assembly150 which couples the upper frame 20 to the tool-side connector plate16. As will be discussed later with reference to FIG. 3, tool-sideconnector plate 16 is connected to a compatible robot-side connectorplate 114.

During a single scan pass, the ultrasonic inspection tool head 10travels along the length of the blade stiffener 2 from one end to theother end, scanning the flange 4, the web 6 and the radiused portions(only radiused portion 8 a is visible in FIG. 2). In accordance with oneembodiment, the inspection probe assembly 14 comprises two phased linearultrasonic transducer arrays for inspecting the flange 4, two phasedlinear ultrasonic transducer arrays for inspecting the web 6, and twophased curved ultrasonic transducer arrays for inspecting the radiusedportions 8 a, 8 b, which ultrasonic transducer arrays are not visible inFIG. 2. The inspection probe assembly 14 further comprises a probehousing assembly 30 which adjustably supports the ultrasonic transducerarrays, as will be explained in more detail later.

Still referring to FIG. 2, the end effector assembly 12 furthercomprises four guide shafts 24 a-24 d each having one end fixedlycoupled (i.e., attached) to the upper frame 20 by means of respectiveshaft mounts 21 a, and a lower frame 22 fixedly coupled to the otherends of guide shafts 24 a-24 d by means of respective shaft mounts 21 b.In a preferred embodiment, the axes of guide shafts 24 a-24 d are allparallel to a Z axis in the frame of reference of the end effectorassembly 12. The end effector assembly 12 further comprises a pair ofbearing block assemblies 26 a and 26 b (best seen in FIG. 2A) which arecoupled to the upper frame 20 by means of respective constant forcespring assemblies 42 a and 42 b (for reasons discussed below withreference to FIG. 28). In addition, bearing block assembly 26 a istranslatably coupled to guide shafts 24 a and 24 b by means ofrespective pairs of linear bearings (not shown in FIG. 2); bearing blockassembly 26 b (visible in FIG. 2A) is translatably coupled to guideshafts 24 c and 24 d by means of respective pairs of linear bearings(not shown). The bearing block assemblies 26 a and 26 b (which supportthe inspection probe assembly 14) can translate in tandem in the Zdirection in the frame of reference of the end effector assembly 12while the constant force spring assemblies 42 a and 42 b exert liftingforces thereon. As best seen in FIG. 2A, the displacement of bearingblock assembly 26 b in the Z direction is measured by an LVDT 18 whichis integrated in the end effector assembly 12. The displacements of thebearing block assemblies 26 a and 26 b will be equal.

As seen in FIG. 2A, the bearing block assembly 26 a comprises arotatable shaft 28 a, while the bearing block assembly 26 c comprises arotatable shaft 28 b. The rotatable shafts 28 a and 28 b have a commonaxis of rotation, which may be treated as the Y axis (perpendicular tothe Z axis) in the frame of reference of the end effector assembly 12.The probe housing assembly 30 of the inspection probe assembly 14 (bestseen in FIG. 2) is clamped to the rotatable shafts 28 a and 28 b.

FIG. 2C is a diagram representing a sectional view taken along a planethat bisects rotatable shaft 28 a. The bearing block assembly 26 acomprises a bearing block 27 in which a pair of coaxial ball bearings 29a and 29 b are seated. The rotatable shaft 28 a is rotatably coupled tothe bearing block 27 by means of ball bearings 29 a and 29 b. Thebearing block assembly 26 b has a similar structure. As a result of thisdesign, the probe housing assembly 30, which is clamped to rotatableshafts 28 a and 28 b, can rotate about the Y axis of the end effectorassembly 12.

As seen in FIG. 2A, each bearing block assembly 26 a, 26 b comprises arespective shaft rotation limit assembly 124 a, 124 b which limits therange of rotation of a respective rotatable shaft 28 a, 28 b. Thestructure of shaft rotation limit assembly 124 a is shown in detail inFIG. 2B. The other shaft rotation limit assembly 124 b has a similarstructure. The shaft rotation limit assembly 124 a comprises a paddle126 having a proximal end fastened to one end of rotatable shaft 28 aand a distal end which is free to rotate about the axis of rotatableshaft 28 a between respective angular position limits. The shaftrotation limit assembly 124 a further comprises a pair of cap screws 128a and 128 b (FIG. 2B) which can be loosened or tightened to adjust theangular position limits. The rotatable shaft 28 a reaches one angularposition limit when the upper surface of the distal end of paddle 126abuts the end of cap screw 128 a and reaches the other angular positionlimit when the lower surface of the distal end of paddle 126 abuts theend of cap screw 128 b.

As further seen in FIG. 2B, the displacement of bearing block assembly26 a along guide shafts 24 a and 24 b is limited by upper shaft collar32 and lower shaft collar 34, which are respectively clamped to guideshaft 24 a. In one implementation, the upper and lower shaft collars 32and 34 are positioned so that the bearing block assembly 26 a is able totravel along guide shafts 24 a and 24 b ±1 inch from a neutral position.This provides a ±1-inch tolerance in the local inspection zone. Withinthis range of displacement, upward displacement is resisted by an uppercompression spring 36 wound around the guide shaft 24 b, while downwarddisplacement is resisted by a lower compression spring 38 wound aroundthe guide shaft 24 b and seated on shaft collar 40 clamped to guideshaft 24 b. The upper and lower compression springs 36 and 38 are usedto center the inspection probe assembly in the neutral position when onan elongated composite member.

In addition, respective constant force spring assemblies 42 a and 42 b(only constant force spring assembly 42 a is visible in FIG. 2B) apply aconstant force regardless of travel distance that counters the weight ofthe inspection probe assembly 14 and allows the latter to “float” in themiddle of the guide shafts 24 a-24 d. This ensures that the inspectionprobe assembly 14 applies very little force to the top of the bladestiffener as the assembly travels along the length of the stiffener. Asis well known in the art, each constant force spring assembly 42 a, 42 bcomprises a rolled ribbon of spring steel designed so that the spring isrelaxed when it is fully rolled up or wound on a reel. In the embodimentdepicted in FIG. 2B, the reels (not visible) are bolted to the upperframe 20 of the end effector assembly 12 and the springs are attached tothe bearing block assemblies 26 a and 26 b on respective sides of theinspection probe assembly 14.

FIG. 3 shows an automated system for inspecting an elongated compositemember such as a blade stiffener in which the ultrasonic inspection toolhead 10 is mounted to a robot 100. Although not shown in FIG. 3, theultrasonic probes incorporated in the ultrasonic inspection tool head 10will be electrically connected to a data acquisition system (also notshown in FIG. 3) by means of electrical cables (not shown in FIG. 3) andwill be in fluid communication with a source of liquid acoustic couplant(e.g., water) by means of hoses.

The ultrasonic inspection tool head 10 is attached to the robot 100 byattaching the tool-side connector plate 16 to a connector 114 of therobot 100. As the ultrasonic inspection tool head 10 is moved along theelongated composite member being inspected, data is sent to the dataacquisition system for processing. Typically, the robot 100 isautomatically controlled to move the ultrasonic inspection tool head 10in a lengthwise direction along the elongated composite member, whilethe data acquisition system generates images of the surface of theelongated composite member to map the inspection probes' responses. Therobot 100 could be used to inspect any number of elongated compositemembers in a variety of industries where detection of flaws or defectsin the structure is required, such as in the aircraft, automotive, orconstruction industries. In particular, if the ultrasonic inspectiontool head 10 is of the type shown in FIG. 2, the robot 100 could be usedto inspect stiffeners of the type shown in FIGS. 1 and 2.

The robot 100 has multi-axis movement capabilities and uses softwaresupport to generate a three-dimensional profile to be used formeasurement and inspection of parts. In particular, the robot 100 shownin FIG. 3 comprises a robot base 102, a carousel 104, a rocker 106(a.k.a. pivot arm), an extension arm 108, a robot hand 110, and a member112 to which the connector 114 is attached. The robot base 102 andcarousel 104 are rotatably coupled by a pivot 116. The carousel 104 androcker 106 are rotatably coupled by a pivot 118. The rocker 106 andextension arm 108 are rotatably coupled by a pivot 120. The rockerextension arm 108 and robot hand 110 are rotatably coupled by a pivot122. The combination of these components provides multiple degrees offreedom, which in turn allows the ultrasonic inspection tool head 10 tobe moved to different locations and in different directions. The robot100 includes one or more positional sensors (not shown) at, or otherwiseassociated with, each of the pivots that provide positional data (X, Y,and Z in three-dimensional space) to the data acquisition system foraccurately locating the probes. In addition, the ultrasonic inspectiontool head 10 could include various numbers of sensors (e.g., one ormore) for acquiring positional data. The probes provide ultrasonic dataindicative of the structure being inspected. As such, the robot 100provides an accurate location of any defects using positional data andultrasonic data acquired during inspection of an elongated compositemember. An example of a robot 100 that could be employed with the probeshown in FIG. 2 is robot Model KR-150 manufactured by Kuka Roboter GmbH(Augsburg, Germany), although any robot or other manipulator capable ofcarrying an ultrasonic inspection tool head and communicating with adata acquisition system could be used.

The data acquisition system may be capable of generating various images,including A-scan, B-scan, and C-scan images of elongated compositemembers based on data collected by the positional sensors and ultrasonicprobes. Furthermore, the data acquisition system may be capable ofgenerating a three-dimensional point cloud based on the data acquired bythe positional sensors and the ultrasonic probes. Thus, a stream ofpositional data may be mapped to a stream of ultrasonic data to generatethe point cloud. The ultrasonic data may include, among otherinformation, data regarding anomalies, defects, irregularities, or otherimperfections in the inspected structure. The data acquisition systemtypically includes a processor or similar computing device operatingunder the control of imaging software so that any defects in theinspected structure may be presented on a display screen. The processorcould be embodied by a computer such as a desktop, laptop, or portableprocessing device capable of processing the data generated by thepositional sensors and ultrasonic probes and creating an image of thescanned data that is shown on a display such as a monitor or otherviewing device. The data acquisition system may generate images of thedata and also allow a user to store and edit previously created images.Therefore, a permanent record of the images may be kept for future useor record keeping. However, it is understood that the data acquisitionsystem need not generate images, as the data acquisition system couldmathematically collect and analyze positional and ultrasonic data that atechnician could use to characterize and locate a flaw based on thedata.

The robot 100 is typically in communication with the data acquisitionsystem to process the data acquired by the positional sensors andultrasonic probes and to display the processed data. In many cases,communications cable(s) (not shown in FIG. 3) transmit data between therobot 100 and the data acquisition system. In other embodiments, thedata may be transmitted between the robot 100 and the data acquisitionsystem via wireless communications. The robot 100 may be directlyconnected to the processor, or indirectly connected, such as via anetwork. In further embodiments, the data acquisition system may belocated proximate to the robot 100, such that remote connections betweenthe robot and data acquisition system are not necessary.

As previously described with reference to FIG. 2, the end effectorassembly 12 comprises a gimbal assembly 150 which couples upper frame 20to the tool-side connector plate 16. The gimbal assembly 150 is designedto enable the end effector frame assembly, comprising upper frame 20,lower frame 22 and guide shafts 24 a-24 d, to rotate about X and Z axes(the X axis being the longitudinal axis of the elongated compositemember being inspected) and translate along a Y axis relative to thetool-side connector plate 16.

FIG. 3A shows an elevational view of the gimbal assembly 150. The gimbalassembly 150 comprises: (1) a pivot joint 152 that allows the endeffector to rotate around the X axis; (2) a pair of linear slides 154that allow the end effector to translate along the Y axis within aspecified range (e.g., ±1 inch; and (3) a rotational joint 156 thatallows the end effector to rotate around the Z axis.

FIG. 3B shows an exploded view of the gimbal assembly 150 depicted inFIG. 3A. The gimbal assembly 150 comprises a pivot bushing 160 which isrotatably coupled to the tool-side connector by means of a pivot pin 158to form the pivot joint 152. The gimbal assembly 150 further comprises alinear slide mounting plate 162, which is translatably coupled to thepivot bushing 160 by means of a pair of linear slides 154. An endeffector base plate 170 (which is part of upper frame 20 seen in FIG. 2)is rotatably coupled to linear slide mounting plate 162 by means of therotational joint 156 indicated in FIG. 3A. As seen in FIG. 3B, therotational joint 156 comprises a threaded bushing 164 (which is fastenedto linear slide mounting plate), an upper thrust bearing 166 a, an upperthrust bearing locating ring 168 a, a lower thrust bearing 166 b, alower upper thrust bearing locating ring, and bolt 172.

The apparatus described above comprises an end effector frame that isrotatable about the X and Y axes and translatable along the Y axis. Aspreviously described, the probe housing assembly 30 is rotatably coupledto the end effector frame by means of a pair of rotatable shafts 28 aand 28 b having a common axis of rotation which is parallel to the Yaxis. Thus the inspection probe assembly 14 is effectively rotatableabout the X, Y and Z axes and translatable in the Y direction. Inaddition, as will now be explained in detail, the probe housing assembly30 comprises means for allowing the respective probes to adjust theirpositions and orientations to take into account variations in size,shape and curvature of the elongated composite member being inspected.

FIGS. 4 and 5 are diagrams respectively representing an isometric viewand an elevation view of the inspection probe assembly 14 in isolationand in accordance with one embodiment. In cases where the structurebeing inspected is a wing blade stiffener comprising a web and a flangethat intersect at an intersection having left and right radiusedportions, the inspection probe assembly 14 comprises threesubassemblies: a web probe subassembly 14A, a flange probe subassembly14B, and a radius probe subassembly 14C, as indicated in FIGS. 4 and 5.

In accordance with the embodiment depicted in FIG. 4, the flange probesubassembly 14B comprises a flange probe platform 46 clamped torotatable shafts 28 a and 28 b (not shown in FIG. 4, but see FIG. 2A) bymeans of a pair of shaft collars 25 (only one of which is visible inFIGS. 4 and 5); the radius probe subassembly 14C comprises a radiusprobe platform 44 translatably coupled to one side of the flange probeplatform 46 by means of a first pair of linear slides 86 a (visible inFIG. 5) and 86 c (visible in FIG. 4) to allow relative verticaldisplacement of the radius and flange probe subassemblies; and the webprobe subassembly 14A comprises a web probe platform 48 translatablycoupled to the other side of the flange probe platform 46 by means of asecond pair of linear slides 86 b (visible in FIG. 5) and 86 d (visiblein FIG. 4) to allow relative vertical displacement of the web and flangeprobe subassemblies. The linear slides 86 a-86 d allow the radius probeplatform 44 and the web probe platform 48 to adjust their verticalpositions relative to the flange probe platform 46 as the inspectionprobe assembly 14 travels along the length of an elongated compositemember. (As used in this and subsequent paragraphs, the terms“horizontal” and “vertical” are with respect to the frame of referenceof the flange probe platform 46.)

Referring again to FIG. 4, the flange probe subassembly 14B furthercomprises a pair of slide bracket assemblies 76 and 78 translatablycoupled to the flange probe platform 46; the radius probe subassembly14C further comprises a pair of slide bracket assemblies 80 and 82translatably coupled to the radius probe platform 44; and the web probesubassembly 14A further comprises a pair of slide bracket assemblies 72and 74 translatably coupled to the web probe platform 46. Each slidebracket assembly is translatably coupled to the associated probeplatform by means of pairs of linear slides. FIG. 5 shows a pair oflinear slides 84 a and 84 b which translatably couple slide bracketassembly 82 to radius probe platform 44; a pair of linear slides 84 cand 84 d which translatably couple slide bracket assembly 78 to flangeprobe platform 46; and a pair of linear slides 84 e and 84 f whichtranslatably couple slide bracket assembly 74 to web probe platform 48.FIG. 4 shows a pair of linear slides 84 g and 84 h which translatablycouple slide bracket assembly 80 to radius probe platform 44; a pair oflinear slides 84 i and 84 j which translatably couple slide bracketassembly 76 to flange probe platform 46; and a pair of linear slides 84k and 84 l which translatably couple slide bracket assembly 72 to webprobe platform 48.

Referring again to FIG. 4, the flange probe subassembly 14B furthercomprises a first dry acoustic couplant housing 54 translatably coupledto slide bracket assembly 78 by means of linear slides 88 c and 88 d;and a second dry acoustic couplant housing 56 translatably coupled toslide bracket assembly 76 by means of linear slides 88 i and 88 j. Theradius probe subassembly 14C further comprises a first radius probehousing 50 translatably coupled to slide bracket assembly 82 by means oflinear slides 88 a and 88 b; and a second radius probe housing 52translatably coupled to slide bracket assembly 80 by means of linearslides 88 g and 88 h. The web probe subassembly 14A further comprises afirst pivot support carriage 58 translatably coupled to slide bracketassembly 74 by means of linear slides 88 e and 88 f; and a second pivotsupport carriage 60 translatably coupled to slide bracket assembly 72 bymeans of linear slides 88 k and 88 l.

Although not shown in the drawings, springs are provided which urge theslide bracket assemblies to translate vertically toward the respectiveprobe platforms, so that the radius probe housings 50, 52, the dryacoustic couplant housings 54 and 56, and the pivot support carriages58, 60 clamp the blade stiffener flange. Springs are also provided tourge the radius probe housings 50, 52, the dry acoustic couplanthousings 54 and 56, and the pivot support carriages 58, 60 to translatehorizontally toward the blade stiffener web. Translation toward theblade stiffener web is limited in each case by a bolt 182 (see, e.g.,FIGS. 4 and 8) which has a threaded portion threadably engaged with athreaded bore in a respective slide bracket assembly and an unthreadedportion that passes through a clearance hole in a Y limit sleeve 180(see FIG. 6A). Bolt 182 is not threadably engaged to Y limit sleeve 180.The Y limit sleeve 180 functions as a stopper. For example, the radiusprobe housing 50 cannot slide past the head of the bolt 182. The minimumgap between the two radius probe housings 50 and 52 can be adjusted byloosening/tightening the bolts 182. This allows the probe to run ontothe end of a blade stiffener more easily by adjusting the gap to closelymatch the thickness of the blade stiffener web.

Still referring to FIG. 4, the web probe subassembly 14A furthercomprises a first web probe housing 62 rotatably coupled to the firstpivot support carriage 58 and a second web probe housing 64 rotatablycoupled to the second pivot support carriage 60. In addition, the firstand second web probe housings 62 and 64 are indirectly translatablycoupled to each other by means of an L-shaped bracket 66 comprising afirst leg 66 a and a second leg 66 b that form a right angle. The firstweb probe housing 62 is translatably coupled to the first leg 66 a ofthe L-shaped bracket 66 by means of a linear slide 68 to enabletranslation along a line parallel to the first leg 66 a; the second webprobe housing 64 is translatably coupled to the second leg 66 b of theL-shaped bracket 66 by means of a linear slide 70 to enable translationalong a line parallel to the second leg 66 b.

In accordance with the embodiment depicted in FIGS. 4 and 5, each probesubassembly comprises a respective pair of ultrasonic transducer arrays.The web probe subassembly 14A comprises a first pair of linearultrasonic transducer arrays respectively housed in the web probehousings 62 and 64 (see linear ultrasonic transducer arrays 90 a and 90b in FIG. 7). The radius probe subassembly 14C comprises a pair ofcurved ultrasonic transducer arrays respectively housed in the radiusprobe housings 50 and 52 (see curved ultrasonic transducer arrays 92 aand 92 b in FIG. 8). The flange probe subassembly 14B comprises a secondpair of linear ultrasonic transducer arrays housed in the flange probeplatform 46 (see linear ultrasonic transducer array 96 a in FIG. 9A andlinear ultrasonic transducer array 96 b in FIG. 9B).

FIG. 6 is a diagram representing a side elevational view of the webprobe subassembly 14A during inspection of a blade stiffener web 6 whichis not perpendicular to the blade stiffener flange 4. Similarly, FIG. 7is a diagram representing an elevational view of a pair of linearultrasonic transducer arrays 90 a and 90 b disposed on opposite sides ofa blade stiffener web 6 which is not perpendicular to the bladestiffener flange 4. It should be understood that the web probe housing62 depicted in FIG. 6 houses the linear ultrasonic transducer array 90 adepicted in FIG. 7 to form a first web probe, while the web probehousing 64 depicted in FIG. 6 houses the linear ultrasonic transducerarray 90 b depicted in FIG. 7 to form a second web probe. As seen inFIG. 6, water is provided inside the web probe housings 62 and 64 by wayof respective water fittings 184.

As seen in FIG. 6, the web probes can rotate to adjust to a changingweb-flange angle of the blade stiffener. This angle changes along thelength of the part. The web probes follow the changing web-flange angle.More specifically, the web probe housings 62 and 64 rotate in tandem bythe same angle about first and second axes of respective pairs of pivotjoints (not visible in FIG. 6) which rotatably couple the web probehousings 62 and 64 to the pivot support carriages 58 and 60respectively. FIG. 6A shows the pivot support carriage 58 having a pairof coaxial pivot points 59, only one of which is visible in the drawing.The pivot support carriage 60 seen in FIG. 6 has a similar pair ofcoaxial pivot points. The pivot points may take the form of revolutejoints.

As seen in FIG. 7, the linear ultrasonic transducer arrays 90 a and 90 bstay in mutually parallel relationship despite rotation of the web probehousings 62 and 64. In addition, the width of the gap between themutually parallel linear ultrasonic transducer arrays 90 a and 90 b willadjust to the varying thickness of the blade stiffener web 6 due to theability of the pivot support carriages 58 and 60 (see FIG. 6) totranslate horizontally toward or away from each other. Furthermore, incases where the blade stiffener has a constant thickness but a non-zerocurvature in a horizontal plane, the pivot support carriages 58 and 60can translate horizontally in the same direction to compensate for thatweb curvature.

The linear ultrasonic transducer arrays 90 a and 90 b (see FIG. 7) canbe operated in a pitch echo mode to ultrasonically inspect the left andright sides of web 6 of a blade stiffener. During scanning, the L-shapedbracket 66 (in conjunction with linear slides 68 and 70 depicted in FIG.4) allows the linear ultrasonic transducer arrays 90 a and 90 b to moveup and down (parallel to the blade stiffener web 6) independently andmove side to side (parallel to the blade stiffener flange 4)independently As the web probe housings 62 and 64 (see FIG. 6) rotate intandem and/or move up/down and/or move closer together/further apart,the L-shaped bracket 66 maintains the parallelism of the linearultrasonic transducer arrays 90 a and 90 b. More specifically, theL-shaped bracket 66 can translate relative to web probe housing 62 alongan axis parallel to the linear ultrasonic transducer array 90 a due tothe translatable coupling of leg 66 a to web probe housing 62. Inaddition, the L-shaped bracket 66 can translate along an axisperpendicular to the linear ultrasonic transducer array 90 b due to thetranslatable coupling of leg 66 b to web probe housing 64. The surfacearea on opposite sides of the blade stiffener web 6 gets smaller orlarger depending on the web-flange angle. When the web-flange anglechanges from acute to obtuse, the coverage of this area changes from onelinear ultrasonic transducer array to the other.

FIG. 8 shows a sectional view of the radius probe subassembly 14Cincorporated in the inspection probe assembly 14 depicted in FIG. 4. Aspreviously described, the radius probe subassembly 14C comprises: a pairof slide bracket assemblies 80 and 82 translatably coupled to the radiusprobe platform 44; a first radius probe housing 50 translatably coupledto slide bracket assembly 82; and a second radius probe housing 52translatably coupled to slide bracket assembly 80. A pair of curvedultrasonic transducer arrays 92 a and 92 b are respectively housedinside radius probe housings 52 and 50 to form first and second radiusprobes for respectively scanning the left and right radiused portions ofa blade stiffener. Springs (not shown in FIG. 8) are provided to urgeslide bracket assemblies 80 and 82 to translate downward and urge radiusprobe housings 50 and 52 to translate laterally toward the bladestiffener web, as a result of which the curved ultrasonic transducerarrays 92 a and 92 b will be disposed near the left and right radiusedportions respectively. The curved ultrasonic transducer arrays 92 a and92 b can be operated in a pitch echo mode to ultrasonically inspect theleft and right radiused portions of the blade stiffener. Water isprovided inside the radius probe housings 50 and 52 by way of respectivewater fittings 184 (only one of which is shown in FIG. 8).

FIGS. 9A and 9B are respective sectional views of the flange probesubassembly 14B incorporated in the inspection probe assembly 14depicted in FIG. 4. In FIG. 9A, the section is taken through the firstlinear ultrasonic transducer array; in FIG. 9B, the section is takenthrough a second linear ultrasonic transducer array. As previouslydescribed, the flange probe subassembly 14B comprises a flange probeplatform 46 which houses a pair of linear ultrasonic transducer arrays96 a (see FIG. 9A) and 96 b (see FIG. 9B) which partly overlapunderneath the web-flange intersection of the blade stiffener. In thealternative, a single linear ultrasonic transducer array of sufficientlength could be substituted for the linear ultrasonic transducer arrays96 a and 96 b, so long as the entire width of the blade stiffener flange4 is covered.

In the implementation depicted in FIGS. 9A and 9B, the linear ultrasonictransducer arrays 96 a and 96 b are acoustically coupled by water to thebottom surface of the blade stiffener flange 4. In addition, the uppersurfaces of the blade stiffener flange 4 are in contact with respectiveblocks 94 a and 94 b of dry acoustic couplant elastomeric materialrespectively housed in the dry acoustic couplant housings 54 and 56. Thedry acoustic couplant elastomeric material (e.g., Aqualene Rubbercommercially available from Innovation Polymers, Kitchener, Ontario,Canada) has an acoustic velocity and an acoustic impedance nearly thesame as water. The blocks 94 a and 94 b of dry acoustic couplantelastomeric material (which mimics the effect of water on ultrasoundwaves) act as delay lines by enabling ultrasound waves to pass through.The system detects getting reflections from the upper surfaces of theblade stiffener flange 4 during pulse echo inspection. The impedencemismatch of the composite material relative to the water creates thisreflection. The elastomeric material serves to mimic the impedance ofwater so the reflection from the upper surface of the blade stiffenerflange 4 looks the same as if water were on the back side of the flange.

The benefits of the elastomeric material are twofold. First, it greatlyreduces the amount of water needed on top of the flange 4. To flood thetop of a wide (e.g., 9-inch) flange would require a very large amount ofwater and increase the size of water pumps, hoses, etc. Second, theelastomeric material creates a calm and stable thin film water sourcefor the outer edge of the flange 4. This allows for fine edge resolutionin the ultrasonic data without seeing signal shifts from waterturbulence on the edge of the part.

As seen in FIG. 9A, water is provided inside the dry acoustic couplanthousings 54 and 56 by way of respective water fittings 184. The presenceof the dry acoustic couplant elastomeric material reduces the size ofthe water column. Good acoustic coupling is maintained by locallyflooding both sides of the part with water inside the perimeters of therespective probes.

As is well known to persons skilled in the art of ultrasonic inspection,water can be fed through one or more supply lines, through the waterfittings 184 and into one or more recesses, such as defined channels ormanifolds, a central cavity, or similar openings that permit the flow ofwater through the housings. A fluid manifold for an inspection probe isthe structure of one or more internal water passages to feed theinterfaces between the ultrasonic transducer arrays and the part beinginspected, thereby coupling ultrasonic signals between the ultrasonictransducer arrays and the part. This process is known as fluid coupling.A fluid manifold may be formed of any number of shapes and merelyrepresents a defined passage from a fluid inlet port to an area throughwhich ultrasound waves propagate for controlling the flow of fluid fromthe fluid inlet port to the area through which ultrasound wavespropagate.

Because contact with a surface of the inspected part may be interrupted,such as along an edge of the part being inspected, the ultrasonicinspection apparatus disclosed herein uses special fluid manifolds inaccordance with a so-called “bubbler method” wherein respective bubblershoes disperse the fluid around each ultrasonic transducer toindependently couple the signal from each ultrasonic transducer to theconfronting surface area of the part under inspection, rather than usinga single cavity to couple all of the ultrasonic transducers. Bubblershoes are described further, for example, in U.S. Pat. No. 7,337,673,the disclosure of which is incorporated by reference in its entiretyherein. By individually coupling each transducer to the surface of thepart, the bubbler shoe compensates for when a portion of the probetravels off an edge of the structure. In such a manner, only thetransducers off the edge of the structure will lose the coupling withthe surface, but the transducers remaining over the surface of thestructure will continue to be independently coupled.

When not inspecting a blade stiffener, the inspection probe assembly 14may be parked on a run-on tool 132 that is designed to serve as anextension of the blade stiffener 2, as depicted in FIGS. 10 and 11. Asbest seen in FIG. 10, the run-on tool 132 comprises a run-on tool web134 and a run-on tool flange 136. In addition, the run-on tool 132 mayhave a web-to-flange angle that matches the web-to-flange angle of anoutboard end of the blade stiffener 2. The probe assembly is designed toaccept a range of part thickness changes. The range should envelope theoutboard end of the stiffeners. The number of run-on tools would likelyaccommodate the ranges of web to flange angles. The result is a seamlessinterface 138 that enables the inspection probe assembly 14 to smoothlyride onto the blade stiffener 2 at the start of an inspection procedure.This keeps the water acoustic coupling stable, maintains edge alignment,and allows for a smooth transition as the inspection probe assembly 14moves from the run-on tool 132 to the blade stiffener 2.

FIG. 12 is a diagram representing an isometric view of a workcell forautomated single-pass ultrasonic inspection of a curved blade stiffener2 supported by a multiplicity of extendible/retractable holding fixtures144 at spaced intervals along the blade stiffener 2. In accordance withone embodiment, each holding fixture comprises a plunger housing 146 anda plunger 148 which is extendible out of or retractable into the plungerhousing 146. The respective amounts of extension of holding fixtures 144can be controlled by a computer (not shown) such that each plungercontacts and thus supports a respective portion of the blade stiffener2. The holding fixtures may be movable to support blade stiffenershaving different lengths and contours.

The exemplary workcell shown in FIG. 12 further comprises a robot 100 ofthe type previously described with reference to FIG. 3, which robot 100travels along a pair of mutually parallel linear tracks 140 and 142. Asthe robot moves along tracks 140 and 142, the ultrasonic inspection toolhead 10 follows the blade stiffener 2, which may be curved as shown. Asthe ultrasonic inspection tool head 10 approaches each holding fixture144 in turn, one or more optical detectors send a first signal to thecomputer, which is programmed to actuate retraction of that holdingfixture, causing it to move out of the way. This allows the ultrasonicinspection tool head 10 to inspect the unsupported span withoutinterference with the retracted holding fixture. After the inspectionprobe moves past the retracted holding fixture, one or more opticaldetectors send a second signal to the computer, which is furtherprogrammed to actuate extension of that holding fixture back to itsoriginal position. The computer-controlled holding fixtures can move inan orchestrated manner that provides a fully automated and seamlessintegrated solution that minimizes stresses induced on the part from anunsupported span or cantilever. The inspection probe assembly 14 mayhave enough compliance to keep load points on a blade stiffener lessthan 500μ Strains during the inspection over a 10-foot unsupported span.

In an alternative embodiment, instead of a central control computercontrolling the states of the holding fixtures 144, each holding fixturemay incorporate a respective microprocessor and one or more opticaldetectors to allow each holding fixture to operate independently.

The automated holding fixtures may be pre-programmed to different partoptions and adjusted by an automated means such as bar code recognitionon a work order. The pre-programmed holding fixtures could be engaged bythe robot program or a programmable logic controller device. The holdingfixtures could be individual robots themselves or simple pogo-typeholding fixtures of the type depicted in FIG. 12.

The system and method disclosed above may be employed in an aircraftmanufacturing and service method 200 as shown in FIG. 13 for inspectingparts of an aircraft 202 as shown in FIG. 14. During pre-production,exemplary method 200 may include specification and design 204 of theaircraft 202 and material procurement 206. During production, componentand subassembly manufacturing 208 and system integration 210 of theaircraft 202 takes place. Thereafter, the aircraft 202 may go throughcertification and delivery 212 in order to be placed in service 214.While in service by a customer, the aircraft 202 is scheduled forroutine maintenance and service 216 (which may also includemodification, reconfiguration, refurbishment, and so on).

Each of the processes of method 200 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof venders, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 13, the aircraft 202 produced by exemplary method 200may include an airframe 218 (comprising, e.g., a fuselage, frames,stiffeners, wing boxes, etc.) with a plurality of systems 220 and aninterior 222. Examples of high-level systems 220 include one or more ofthe following: a propulsion system 224, an electrical system 226, ahydraulic system 226, and an environmental control system 230. Anynumber of other systems may be included. Although an aerospace exampleis shown, the principles disclosed herein may be applied to otherindustries, such as the automotive industry.

Apparatus and methods embodied herein may be employed during any one ormore of the stages of the production and service method 200. Forexample, elongated composite members fabricated during productionprocess 208 may be inspected using the inspection system disclosedherein. Also, one or more apparatus embodiments, method embodiments, ora combination thereof may be utilized during the production stages 208and 210, for example, by substantially expediting assembly of orreducing the cost of an aircraft 202. Similarly, one or more ofapparatus embodiments, method embodiments, or a combination thereof maybe utilized while the aircraft 202 is in service, for example andwithout limitation, during maintenance and service 216.

While ultrasonic inspection systems have been described with referenceto various embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the teachingsherein. In addition, many modifications may be made to adapt theteachings herein to a particular situation without departing from thescope thereof. Therefore it is intended that the claims not be limitedto the particular embodiments disclosed herein.

The invention claimed is:
 1. A method for automated non-destructiveinspection of a stationary elongated composite member in a single pass,comprising: supporting the elongated composite member using amultiplicity of holding fixtures disposed at intervals along a length ofthe elongated composite member, each holding fixture having an extendedposition in which the elongated composite member is supported and aretracted position in which the holding fixture is separated from theelongated composite structure; moving an inspection probe assembly alonga length of the elongated composite member from one end of the elongatedcomposite member to another end of the elongated composite member;inspecting the elongated composite member as the inspection probeassembly moves along the length of the elongated composite member;moving each holding fixture to the retracted position in sequence toallow the inspection probe assembly to pass by as the inspection probeassembly moves along the length of the elongated composite member; andextending each retracted holding fixture back to the extended positionafter the inspection probe assembly has passed by.
 2. The method asrecited in claim 1, further comprising: detecting the inspection probeassembly as the inspection probe assembly approaches the holding fixturein the extended position; sending a first signal in response todetecting approach of the inspection probe assembly; receiving the firstsignal at a control computer; and sending a retract command from thecontrol computer that causes the holding fixture to move from theextended position to the retracted position in response to receiving thefirst signal at the control computer.
 3. The method as recited in claim2, further comprising: detecting the inspection probe assembly as theinspection probe assembly passes by the holding fixture in the retractedposition; sending a second signal in response to detecting passage ofthe inspection probe assembly; receiving the second signal at thecontrol computer; and sending an extend command from the controlcomputer that causes the holding fixture to move from the retractedposition to the extended position in response to receiving the secondsignal at the control computer.
 4. The method as recited in claim 3,further comprising stopping extension of the holding fixture when theholding fixture contacts the elongated composite member.
 5. The methodas recited in claim 1, wherein the stationary elongated composite membercomprises a web portion, a flange portion and a radiused portion, andinspecting the elongated composite member comprises concurrentlyinspecting the web portion, the flange portion and the radiused portionof the elongated composite member as the inspection probe assembly movesalong the length of the elongated composite member.
 6. The method asrecited in claim 5, wherein concurrently inspecting the web portion, theflange portion and the radiused portion of the elongated compositemember comprises concurrently ultrasonically inspecting the web portion,the flange portion and the radiused portion of the elongated compositemember using a multiplicity of ultrasonic transducer arrays.
 7. Themethod as recited in claim 1, wherein inspecting the elongated compositemember comprises ultrasonically inspecting the elongated compositemember.
 8. The method as recited in claim 1, further comprisingadjusting an orientation of the inspection probe assembly in dependenceon a changing orientation of the elongated composite member as theinspection probe assembly moves along the length of the elongatedcomposite member.
 9. The method as recited in claim 1, furthercomprising adjusting a configuration of the inspection probe assembly independence on a changing shape of the elongated composite member as theinspection probe assembly moves along the length of the elongatedcomposite member.
 10. The method as recited in claim 1, furthercomprising adjusting relative positions of probe subassemblies of theinspection probe assembly in dependence on changing dimensions of theelongated composite member as the inspection probe assembly moves alongthe length of the elongated composite member.
 11. A method for automatedultrasonic inspection of a stationary elongated composite member havinga web portion, a flange portion and a radiused portion, in a singlepass, comprising: supporting the elongated composite member using amultiplicity of holding fixtures disposed at intervals along a length ofthe elongated composite member, each holding fixture having an extendedposition in which the elongated composite member is supported and aretracted position in which the holding fixture is separated from theelongated composite structure; moving an inspection probe assembly alonga length of the elongated composite member from one end of the elongatedcomposite member to another end of the elongated composite member, theprobe assembly comprising a multiplicity of ultrasonic transducerarrays; concurrently ultrasonically inspecting the web portion, theflange portion and the radiused portion of the elongated compositemember using the multiplicity of ultrasonic transducer arrays as theinspection probe assembly moves along the length of the elongatedcomposite member; moving each holding fixture to the retracted positionin sequence to allow the probe assembly to pass by; and extending eachretracted holding fixture back to its extended position after the probeassembly has passed by.
 12. The method as recited in claim 11, furthercomprising adjusting the positions of the multiplicity of ultrasonictransducer arrays to take into account variations in the shape andlocation of the elongated composite member along the length as theinspection probe assembly moves along the length of the elongatedcomposite member.
 13. The method as recited in claim 12, wherein saidadjusting step comprises adjusting respective angles of first and secondlinear ultrasonic transducer arrays as an angle between web and flangeportions of the elongated composite member changes along the its length.14. The method as recited in claim 12, wherein said adjusting stepcomprises adjusting an elevation of an end effector assembly thatsupports the inspection probe assembly as a curvature of the elongatedcomposite member in an elevation direction changes along the its length.15. A non-destructive inspection system comprising: an elongatedcomposite member having a web portion, a flange portion and a radiusedportion; a multiplicity of holding fixtures disposed at respectivepositions at intervals along a length of the elongated composite member,each holding fixture comprising a plunger housing and a plunger which isextendible out of or retractable into the plunger housing, wherein atleast one plunger is retracted and not in contact with the elongatedcomposite member, while other plungers are extended, in contact with andprovide support to the elongated composite member; and an inspectiontool head comprising an end effector assembly and an inspection probeassembly that is carried by the end effector assembly, wherein theinspection probe assembly comprises a web probe, a flange probe and aradius probe positioned to interrogate the web portion, the flangeportion and the radiused portion respectively of a section of theelongated composite member where the at least one plunger would contactthe elongated composite member if the at least one plunger wereextended.
 16. The non-destructive inspection system as recited in claim15, wherein each of the web probe, the flange probe and the radius probecomprises a respective ultrasonic transducer array acoustically coupledto the web portion, the flange portion and the radiused portionrespectively of the section of the elongated composite member.
 17. Thenon-destructive inspection system as recited in claim 15, furthercomprising: a multiplicity of optical detectors positioned for detectinga position of the inspection probe assembly; and a computer configuredto control the positions of the holding fixtures in dependence onsignals received from the optical detectors.
 18. The non-destructiveinspection system as recited in claim 17, wherein the computer isconfigured to send a retract command to at least one holding fixture inresponse to receiving a signal from an optical detector that theinspection probe assembly is approaching the at least one holdingfixture.
 19. The non-destructive inspection system as recited in claim17, wherein the computer is configured to send an extend command to atleast one holding fixture in response to receiving a signal from anoptical detector that the inspection probe assembly has passed the atleast one holding fixture.
 20. The non-destructive inspection system asrecited in claim 15, wherein at least one holding fixture comprises atleast one optical detector and a microprocessor configured to controlthe position of the at least one holding fixture in dependence on asignal received from the at least one optical detector.